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Data from banded penguins suffer from fatal flaw

The common practice of collecting data by flipper-banding penguins is …

Many research groups use penguins, one of the top predators in the Southern Oceans, as ecological indicators. For ease of identification and data collection, researchers often attach flipper-bands on penguins, a practice that dates back to Antarctic expeditions of the early 1900s. Over the last century, scientists have collected considerable amounts of data from flipper-banded penguins, which has greatly influenced our understanding of the effects of climate change in marine ecosystems. Sadly, that data might not be reliable. A paper in a recent issue of Nature reveals that flipper-banded penguins live quite differently than unbanded birds.

This news is not exactly shocking, as ornithologists have been calling for an end to banding for over a decade. Short- to medium- length studies on the effects of flipper-banding have shown that banded birds had poorer survival rates. In a five year study published in a 2004 issue of Proceedings of Royal Society Biological Sciences, Michel Gauthier-Clerc and his group reported that flipper-banded king penguins had “later arrival at the colony for courtship in some years, lower breeding probability and lower chick production.“ Similarly, Katie Dugger and her colleagues reported in a 2006 paper in the Auk that flipper-banded penguins saw yearly survival drop by 11-13 percent over a three-year period.

However, there are also studies that indicate that the dangers of banding are limited. In particular, many groups report that banding’s negative effects are only significant in freshly banded birds. In the Dugger paper mentioned above, the authors found that, over a seven-year period, there was high annual variability in survival for banded birds, including years of high survival. Likewise, in 2009, Pamela Fallow and her colleagues wrote in the Journal of Wildlife Management that “long-term banded penguins did not exhibit differences to their unbanded counterparts in most variables examined.”

While researchers like Fallow may not support the banding practice, their data showed that certain differences between banded and unbanded penguins evened out after the initial period. Some researchers, like Christophe Barbraud and Henri Weimerskirch, dealt with the ambiguity by continuing to use banding, but excluded data collected in the initial years in their Nature 2001 paper.

The latest Nature paper challenges that practice, as the authors demonstrate in a long-term study that flipper-banding significantly alters the life of a penguin. Claire Saraux, the lead author, and her team used subcutaneous electronic tags to track 100 king penguins. They attached metal flipper-bands on 50 of those penguins. Over 10 years of observation, they found that banding influenced survival and breeding rates, which would skew data collection.

In terms of survival, banded penguins had a 16 percent lower rate over the entire 10 years, but there is a breakpoint at 4.5 years. In the first 4.5 years, banded penguins actually had a 30 percent higher mortality rate. After that, the difference in mortality between banded and unbanded birds levels off. The authors propose that flipper-banding acts as an artificial selector for the strongest penguins, creating a bias in data collected from banded birds.

Over the decade, banded birds were less successful in breeding. Banded penguins produced a total of 47 chicks, while unbanded penguins had 80 chicks. The authors observed that banded birds took longer to arrive at breeding grounds, which can account for the difference in their success.

The authors also found a possible reason for why some previous research groups observed negligible survival differences between banded and unbanded penguins after the initial year. In their own decade-long study, there was a three-year period where the environment was exceptionally favorable for penguins. During that time, unbanded and banded penguins displayed insignificant differences. The conditions were so good that penguins might have been able to compensate from the disadvantage of having a flipper-band.

Saraux and her colleagues have cast even more doubt on the practice of flipper-banding penguins. The behavior of banded penguins could very well be a reflection of a metal accessory that potentially injures flipper tissue and impedes swimming, rather than environmental changes.

On top of that, banding could be exceptionally harmful for vulnerable birds like those recovering from oil spills. After an oil spill off Cape Town in June 2000, roughly 20,000 African penguins were rehabilitated and ﬂipper-banded before being released. Those penguins might have done better without the added burden of a flipper-band. Since there are alternatives to flipper-banding, it could be worthwhile to invest in newer techniques for the sake of obtaining more reliable data and avoiding damage to wildlife.

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Yun Xie
Yun Xie / Yun Xie is a contributing science writer at Ars, where she covers the latest advancements in science and technology for Ars. She currently works in scientific communications, policy, and review. Emailreenxie@gmail.com//Twitter@yun_xie